On Tuesday, Sharif was at the United States Institute of Peace in Washington.
"Recently our political parties in a national conference declared the use of drones is not only a continued violation of our territorial integrity but also detrimental to our resolve at efforts in eliminating terrorism from our country," Sharif said.
"This issue has become a major irritant in our bilateral relationship as well. I therefore would stress the need for an end to the drone attacks."
Sharif has previously called for an end to the U.S. drone program in Pakistan, where it has stirred deep anger, and will raise the issue with Obama on Wednesday, said Aizaz Ahmad Chaudhry, a spokesman for the Pakistani Foreign Ministry.
"The government of Pakistan believes drone strikes are against international law and the sovereignty of Pakistan," Chaudhry told CNN. "Drone strikes are counterproductive to fighting terrorism."
Pakistan wants to persuade the United States to stop using drones, he said.
"International opinion is against drone strikes, not just here in Pakistan, but in the world," Chaudhry said. "This opinion is strengthening."
Adding to the pressure, Human Rights Watch also released a report on U.S. drone attacks Tuesday -- this one focusing on Yemen.
Letta Taylor, a senior counterterrorism researcher for Human Rights Watch, said the group found at least two clear cases of violations of international laws of war, but those did not reach war crimes status.
The group said four of the six attacks it had investigated "may have violated the laws of war."
Lack of U.S. disclosure
Based on extensive field research, the reports underlined the difficulties of gathering information on attacks in dangerous areas of Pakistan and Yemen.
"We found that despite assurances from President Obama that (the U.S. government is) doing its utmost to protect civilians from harm, that in fact in many cases it is killing innocent civilians, even dozens of them, if not more," Taylor said.
And both reports noted the U.S. government's unwillingness to talk about the cases.
The lack of information from U.S. authorities, Amnesty said, makes it impossible "to reach firm conclusions about the context in which the U.S. drone attacks on Mamana Bibi and on the 18 laborers took place, and therefore their status under international law."
White House Press Secretary Jay Carney rejected the idea that the United States has violated any laws.
"To the extent these reports claim that the U.S. has acted contrary to international law we would strongly disagree," he said at a press briefing Tuesday. "The administration has repeatedly emphasized the extraordinary care that we take to make sure that counterterrorism actions are in accordance with all applicable law."
The U.S. government has said strikes by the unmanned aircraft are a necessary part of the fight against militant groups. In May, Obama defended the drone program and disclosed the guidelines determining its use.
He said drones would be deployed only when there is an imminent threat, no hope of capturing the targeted terrorist, "near certainty" that civilians wouldn't be harmed and "no other governments capable of effectively addressing the threat."
Civilian victims in Yemen